Implantable microstimulator having a battery unit and methods of use therefor

ABSTRACT

An implantable microstimulator arrangement includes at least one implantable microstimulator unit; an implantable battery unit separate from the implantable microstimulator unit(s); and at least one lead coupling the microstimulator unit(s) to the battery unit. The microstimulator unit(s) are operated to treat body tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 11/056,762 filed on Feb. 11, 2005, now U.S. Pat. No. 7,840,279,which is incorporated herein by reference.

FIELD

The invention is directed to implantable microstimulator arrangementshaving a separate implantable battery unit and methods of using themicrostimulator arrangements.

BACKGROUND

Implantable microstimulators have been developed to provide therapy fora variety of disorders, as well as other treatments. For example,implantable microstimulators can be used in neurological therapy bystimulating nerves or muscles, for urinary urge incontinence bystimulating nerve fibers proximal to the pudendal nerves of the pelvicfloor, for erectile and other sexual dysfunctions by stimulating thecavernous nerve(s), for reduction of pressure sores or venous stasis,etc.

Implantable microstimulators, such as the BION® device (available fromAdvanced Bionics Corporation, Sylmar, Calif.), have exposed electrodesand a small, often cylindrical, housing that contains the electroniccircuitry and power source that produce electrical pulses at theelectrodes for stimulation of the neighboring tissue. It is oftenpreferable that the microstimulator be as small as possible to providestimulation to the desired tissue without substantially disturbingsurrounding tissue. Therefore, the battery for the microstimulator istypically small and often rechargeable. In many instances, the batterymust be recharged every day or several days, at least in part because ofits small size.

BRIEF SUMMARY

One embodiment is an implantable microstimulator arrangement thatincludes at least one implantable microstimulator unit; an implantablebattery unit separate from the implantable microstimulator unit(s); andat least one lead coupling the microstimulator unit(s) to the batteryunit.

Another embodiment is an implantable microstimulator arrangement thatincludes at least one implantable battery unit; a plurality ofimplantable microstimulator units; a plurality of lead connectors; and aplurality of leads that couple the microstimulator units to the batteryunit(s) using the lead connectors.

Yet another embodiment is a method of treating body tissue. The methodincludes implanting at least one microstimulator unit into a body in theproximity of the body tissue to be treated. A separate battery unit isalso implanted into the body and the battery unit is coupled to themicrostimulator unit(s) using at least one lead. The microstimulatorunit(s) are then operated to treat the body tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read, inassociation with the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of one embodiment of amicrostimulator arrangement, according to the invention;

FIG. 2 is a schematic plan view of another embodiment of amicrostimulator arrangement according to the invention;

FIG. 3 is a schematic overview of one embodiment of components for asystem for microstimulation of body tissues, according to the invention;

FIG. 4 is a schematic overview of another embodiment of components for asystem for microstimulation of body tissues, according to the invention;

FIG. 5 is a schematic cross-sectional view of one embodiment of amicrostimulator unit, according to the invention;

FIG. 6 is a schematic cross-sectional view of another embodiment of amicrostimulator unit, according to the invention;

FIG. 7 is a schematic cross-sectional view of a third embodiment of amicrostimulator unit, according to, the invention;

FIG. 8 is a schematic cross-sectional view of one embodiment of a leadconnector and leads, according to the invention; and

FIG. 9 is a schematic cross-sectional view of another embodiment of alead connector and leads, according to the invention.

DETAILED DESCRIPTION

The present invention is directed to the area of implantablemicrostimulators and methods of using the microstimulators. Animplantable microstimulator can include a separate implantable batteryunit that is coupled to one or more implantable microstimulator units bya lead or a number of leads and lead connectors.

Previously, implantable microstimulators have been made with batteriesdisposed in the housing of the microstimulator. Examples of suchmicrostimulators are found in U.S. Pat. Nos. 5,193,539; 5,193,540;5,312,439; 6,051,017; and 6,609,032; U.S. Patent Application PublicationNo. 2004/059392; PCT patent applications Publication Ser. Nos. 98/37926;98/43700; and 98/43701; and U.S. patent application Ser. No. 11/040,209,entitled “Implantable microstimulator with plastic housing and methodsof manufacture and use,” filed on Jan. 20, 2005, all of which areincorporated herein by reference.

FIG. 1 illustrates one embodiment of a microstimulator arrangement 100that includes an implantable microstimulator unit 102, an implantablebattery unit 104, and .a lead 106 extending between the microstimulatorunit and the battery unit. Both the microstimulator unit 102 and thebattery unit 104 are implantable. The microstimulator unit 102 can beimplanted in contact with or near the tissue to be stimulated. Thebattery unit 104 can be implanted in a position, for example, near theskin, that is more accessible for charging or replacement, from which itis easier to remove the battery unit, if desired, or which is morecomfortable for the patient.

FIG. 2 illustrates a microstimulator arrangement 100 with a singlebattery unit 104 and multiple microstimulator units 102 connected to thebattery unit by multiple leads 106 and lead connectors 105. It will berecognized that any number of microstimulators units 102 can be used andthat any number of leads 106 can be coupled to a lead connector 105.Furthermore, it will be recognized that the microstimulator arrangementcan include more than one battery unit. Each of the individualmicrostimulator units can be implanted anywhere in the body of thepatient. The microstimulator units can be used to stimulate the sametissue or different tissue regions.

The battery unit will typically include at least a housing and a powersource. Any power source can be used in the battery unit 104. Forexample, the battery unit can contain at least one . battery such as aprimary battery or a rechargeable battery. Examples of other powersources for the battery unit include super capacitors, nuclear or atomicbatteries, mechanical resonators, infrared collectors, thermally-poweredenergy sources, flexural powered energy sources, bioenergy powersources, fuel cells, bioelectric cells, osmotic pressure pumps, and thelike including the power sources described in U.S. Patent ApplicationPublication. No. 2004/0059392, incorporated herein by reference.

If the power source 120 of the battery unit 104 is a rechargeablebattery or other rechargeable power source, the battery may be rechargedusing an optional antenna 124 (see FIGS. 3 and 4), if desired. Theoptional antenna 124 is disposed in or on the housing of the batteryunit 104. Power can be provided to the rechargeable power source forrecharging by inductively coupling the rechargeable power source throughthe antenna 124 to a recharging unit 210 (see FIGS. 3 and 4) external tothe patient.

Communication and/or control signals for the microstimulator arrangementare optionally transmitted via the. antenna 124 to the battery unit (asillustrated in FIG. 3) and can be carried to the microstimulator unit102 by modulating the electrical power supplied by the battery unit 104.The battery unit 104 can also optionally include electronic circuitry,such as a DC/AC converter or a portion of the electronic subassembly,described below, for the operation of the microstimulator unit.Electrical power delivered from the battery unit 104 to themicrostimulator unit 102 can be DC power or it may be converted from DCto AC in the battery unit and the AC may then be delivered via aconnecting lead structure and to the microstimulator ormicrostimulators.

Schematic examples of suitable microstimulator units are illustrated inFIGS. 5, 6, and 7. It will be understood that a variety of othermicrostimulator unit configurations can be used. The microstimulatorunit 102 typically includes a housing 150, one or more electrodes (forexample, electrodes 114, 116), and an electronic subassembly 122. Whenthe microstimulator unit includes only one electrode (see, for example,FIG. 7), the second, indifferent, electrode can be associated with thebattery unit 104, lead 106, or lead connector 105; for example, thesecond, indifferent, electrode can be the case of the battery unit orlead connector. Electrical current is emitted by one or more electrodes(for example, the two electrodes 114, 116 of FIGS. 4, 5) to stimulatetissue such as, for example, motor nerve fibers, muscle fibers, or otherbody tissues near the microstimulator unit.

The housing 150 of the microstimulator unit 102 can be formed of anymaterial that resists the transport of moisture into the interior of thehousing and is sufficiently sturdy to protect the components on theinterior of the housing from damage under expected implantation andusage conditions. Examples of such materials include metals, alloys,ceramics, and plastics. Examples of microstimulator units with plastichousings are disclosed in U.S. patent application Ser. No. 11/040,209,entitled “Implantable microstimulator with plastic housing and methodsof manufacture and use,” filed on Jan. 20, 2005, incorporated herein byreference. In at least some embodiments, the housing 150 is formed usingtwo or more different materials that are joined together. For example, aportion of the housing can be made of a metal or alloy and a secondportion of the housing can be made of ceramic. These portions can bejoined together by, for example, brazing.

The housing 150 can have any shape including, for example, cylindrical,conical, parallelepiped, cubic, and the like. In at least someembodiments, a cylindrical shape is preferred. The lateralcross-sectional dimensions can be the same or can vary along the lengthof housing. In one embodiment, the housing has a cylindrical shape witha uniform diameter along the length of the housing. The uniform diametercan be, for example, up to 8 mm in diameter and, more preferably, theuniform diameter may range between about 1 to 5 mm in diameter. Inanother embodiment, the housing is a cylinder that is wider at the endsand narrower in the middle or the housing is a cylinder that is wider inthe middle and narrower at the ends.

Optionally, the housing can be covered, in full or in part, with acoating. The coating can be provided to improve or alter one or moreproperties of the housing including, for example, biocompatibility,hydrophobicity, moisture permeability, leaching of material into or outof the housing, and the like. The optional coating can be a polymermaterial, inorganic material, or organic material. As an example, thehousing may be coated with an inorganic material, such as, for example,silicon dioxide, silicon nitride, titanium dioxide, or the like, toreduce moisture permeability. As another example, a silicone coating maybe used to cover the housing to improve biocompatibility. In yet anotherexample, a coating can be applied which contains a compound, such as,for example, a drug, prodrug, hormone, or other bioactive molecule, thatcan be released over time when the microstimulator is implanted. (Inanother embodiment, a plastic housing itself may include such a compoundto be released over time after implantation.) In some embodiments, thecoating includes two or more layers of the same or different materials.For example, alternating layers of inorganic materials can be depositedas a coating to improve resistance to moisture transport through thehousing.

The formation of the coating can be accomplished using any methodincluding, for example, dip-coating, sputtering, reactive sputtering,physical or chemical vapor deposition, spray coating, and the like. Thecoating can be applied before the other microstimulator components havebeen assembled within the housing or at any other point in themicrostimulator manufacturing process including applying the coatingafter the microstimulator has been completely assembled. Typically, thecoating is non-conductive.

The one or more electrodes 114, 116 of the microstimulator unit can beformed using any conductive material including metals and alloys.Preferably, the electrodes are formed of material(s) that does notsubstantially corrode under the operating conditions and in theoperating environment for the expected lifetime of the microstimulatorunit. Examples of suitable materials include conductive materials suchas, for example, titanium, iridium, platinum, platinum/iridium alloy,stainless steel, and the like.

The electrodes 114, 116 can be formed entirely of a single conductivematerial, such as a metal or alloy, or one or both of the electrodes canbe formed using a combination of conductive materials such as, forexample, a conductive coating over a bulk metallic electrode. As anotherexample, one or both of the electrodes 114, 116 can be formed from apolymeric material that is at least partially, or fully, coated with, aconductive coating, such as a metal, alloy, or conductive oxide (e.g.,iridium oxide) coating.

In one embodiment, each of the one or more electrodes is a solid bodythat fits into one end of the housing 150, as illustrated for example inFIG. 5. The electrode can be coupled to the battery and electronicsubassembly by attaching a conductor 126, 127 to a surface of theelectrode. As an alternative, one or both of the electrodes 114 or 116can include a hole through the electrode body. A conductor from theelectronic subassembly 122 or power source 120 can then be guidedthrough the hole and the lead can be attached to a conductive exteriorsurface of the electrode. The attachment of the lead to the electrodecan be performed by any method including, for example, soldering orlaser welding. Generally, if a hole through the electrode body isutilized, the hole is also sealed prior to, simultaneously with, orafter the attachment of the lead to the electrode surface to maintain ahermetically-sealed environment within the housing. Other methods andarrangements for attaching a lead to each electrode can be used.

In one embodiment, one or both of the electrodes 114, 116 may bepositioned at ends of the housing 150 as illustrated, for example, inFIGS. 5, 6, and 7. In at least some embodiments, the electrodes 114, 116are disposed at opposing or opposite ends of the housing 150. Forexample, the electrodes 114, 116 can be disposed at opposite ends of acylindrical housing, as illustrated in FIG. 5.

One of the electrodes (e.g., electrode 116 of FIG. 5), or a portion ofthe housing as illustrated in FIGS. 6 and 7, defines an opening throughwhich lead 106 can pass. Preferably, this opening is hermetically sealedfor implantation and operation of the microstimulator arrangement.Optionally, as illustrated in FIG. 5 a non-conductive region 154 can beformed around this opening to prevent or resist conduction ofelectricity between the electrode 116 and the lead 106. In otherembodiments, the sheathing about the lead is sufficient to prevent orresist conduction of electricity.

In some embodiments, one or both of the electrodes 114, 116 can beformed around the circumference of the housing. One example of such anarrangement is illustrated in FIG. 6. In this example, the electrode 114forms a ring around the housing 150. The electrode 114 can be partiallyor fully embedded in the housing 150 or the electrode 114 can be formedover the housing 150.

The electronic subassembly 122 provides the electronics used to operatethe microstimulator and generate the electrical pulses at the electrodes114, 116 to produce stimulation of the body tissues. FIGS. 3 and 4illustrate two embodiments with components of the electronic subassemblyand associated units. It will be understood that the electronicsubassembly can include more, fewer, or different components and canhave a variety of different configurations including thoseconfigurations disclosed in the microstimulator references cited above.Some or all of the components of the electronic subassembly can bepositioned on one or more circuit boards or similar carriers within thehousing, if desired. Some or all of the components of the electronicsubassembly can be disposed in the microstimulator unit or portions ofthe electronic subassembly (e.g., the processor 204) can be disposed inthe battery unit.

In the illustrated embodiments, a processor 204 is provided to controlthe timing and electrical characteristics of the microstimulator. Forexample, the processor can, if desired, control one or more of thetiming, periodicity, strength, duration, and waveform of the electricalpulses provided at the electrodes. Any processor can be used and theprocessor can be as simple as a electronic device that produces pulsesat a regular interval or the processor can be capable of receiving andinterpreting instructions from an external programming unit 208 thatallow modification of pulse characteristics.

In the illustrated embodiment of FIG. 3, the processor receives signalsvia the power source 120. In this embodiment, a programming unit 208 isused to determine what signals should be provided to the microstimulatorarrangement 100. The programming unit 208 sends signals to a telemetryunit 206 which then broadcasts signals to the power source 120 via theoptional antenna 124. The power source can, for example, overlay thesesignals on the power provided to the microstimulator unit 102.

In another embodiment illustrated, for example, in FIG. 4, the processor204 is coupled to a receiver 202 which, in turn, is coupled to anantenna 224. This allows the processor to receive instructions from anexternal source, such as the telemetry unit 206 and programming unit208, to direct the pulse characteristics. In at least some embodiments,when multiple microstimulator units are provided, the receivers 202 ofthe microstimulator units can be tuned to different frequencies or eachmicrostimulator unit may be identified by a unique identifier that istransmitted by the telemetry unit to indicate which microstimulator unitis addressed.

In these illustrated embodiments, the antenna 124 or 224 is capable ofreceiving signals (e.g., infrared or RF signals) from an externaltelemetry unit 206 which is programmed by a programming unit 208. Theprogramming unit 208 can be external to, or part of, the telemetry unit206. The telemetry unit 206 can be, for example, a device that is wornon the skin of the patient, or can be carried by the patient and canhave a form similar to a pager or cellular phone, if desired. As anotheralternative, the telemetry unit may not be worn or carried by thepatient but may only be available at a home station or at a clinician'soffice. The programming unit 208 can be any unit that can provideinformation to the telemetry unit for transmission to the implantedmicrostimulator. The programming unit 208 can be part of the telemetryunit 206 or can provide signals or information to the telemetry unit viaa wireless or wired connection. One example of a suitable programmingunit is a computer operated by the patient or clinician to send signalsto the telemetry unit.

The signals sent to the processor 204 can be used to modify or otherwisedirect the operation of the microstimulator. For example, the signalsmay be used to modify the pulses of the microstimulator such asmodifying one or more of pulse duration, pulse frequency, pulsewaveform, and pulse strength. The signals may also direct themicrostimulator to cease operation or to start operation or to startcharging the battery.

Optionally, the microstimulator unit or battery unit (or both) caninclude a transmitter (not shown) coupled to the processor and antennafor transmitting signals back to the telemetry unit 206 or another unitcapable of receiving the signals. For example, the microstimulator maytransmit signals indicating whether the microstimulator is operatingproperly or not or indicating when the battery needs to be charged. Theprocessor may also be capable of transmitting information about thepulse characteristics so that a patient or clinician can determine orverify the characteristics.

The optional antennas 124, 224 can have any form. In one embodiment, theantenna 124 comprises a coiled wire that is wrapped at least partiallyaround the power source in the battery unit 104. In another embodiment,the antenna 224 comprises a coiled wire that is wrapped at least,partially around the electronic subassembly within the housing, asillustrated, for example, in FIGS. 5, 6, and 7.

Any method of manufacture of the microstimulator unit can be used. Forexample, the electronic subassembly and antenna can be manufactured in amanner similar to that described in U.S. Patent Application PublicationNo. 2004/0059392. These components can then be placed inside the housing(or, alternatively, the housing can be formed, e.g., molded, around thecomponents). The electrodes can be attached to the housing, for example,screwed into opposite ends of the housing, and leads from the electronicsubassembly can be attached to the electrodes. Coatings on theelectrodes or housing, if any, can be applied at appropriate pointsduring the manufacturing process.

Each lead 106 of the microstimulator arrangement 100 includes one ormore conductors disposed within a non-conductive, biocompatiblesheathing. A lead can be removably or non-removably coupled or couplableto a microstimulator unit 102, battery unit 104, or lead connector 105.FIG. 1 illustrates one embodiment in which the lead 106 is non-removablycoupled to a microstimulator unit 102 and a battery unit 104. In otherembodiments, one end of the lead 106 can be non-removably coupled to amicrostimulator unit 102, battery unit 104, or lead connector 105 andthe other end of the lead 106 can be removably coupled or couplable to amicrostimulator unit 102, battery unit 104, or lead connector 105. Inyet other embodiments, both ends of the lead 106 are removably coupledor removably couplable.

When the lead is non-removably coupled, the conductors 152 of the lead106 are typically attached to a power source, electronic subassembly, orother component. Examples of removable coupling of a lead 106 to a leadconnector 105 are illustrated in FIGS. 8 and 9. The end of the lead 106can have a male plug 180 with one or more conductive regions 184, 186that can mate with corresponding conductive region(s) 185, 187 of afemale receptacle 182 of the lead connector 105. Conductor(s) 193, 194within the lead connector 105 connect the corresponding conductiveregion(s) 185, 187. An optional sealing member 190 can be providedaround the lead to facilitate sealing of the receptacle 182 from fluids.Preferably, a hermetic seal is made when the male plug is plugged intothe female receptacle. Optionally, the lead connector can include asuture hole that can be used to suture the lead, and optionally the leadconnector, in place. It will be recognized that a similar arrangementwith a male plug and female receptacle can be provided for removablycoupling a lead 106 to a microstimulator unit 102 or battery unit 104.It will also be recognized that a lead could include a female receptacleand the microstimulator unit, battery unit, or lead connector couldinclude a corresponding male plug.

A lead connector 105 can connect two or more leads. For example, leadconnectors for connecting three leads, one lead that directly orindirectly comes from the battery unit and two leads that each directlyor indirectly proceed to one or more microstimulator units, areillustrated in FIGS. 8 and 9. It will be recognized that lead connectorscan be made which allow connection of more than two leads that proceeddirectly or indirectly to microstimulator units.

The microstimulator arrangement or portions of the microstimulatorarrangement can be implanted individually or together into the bodytissue using a variety of methods including surgical methods. In someembodiments, portions of the microstimulator arrangement, such as themicrostimulator leads, can be implanted using a hypodermic needle orother insertion cannula. Examples of insertion techniques can be foundin U.S. Pat. No. 6,051,017.

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

1. An implantable microstimulator arrangement, comprising: a pluralityof implantable microstimulator units, each of the plurality ofmicrostimulator units individually comprising a first housing, at leastone electrode disposed on, or as part of, the first housing, and anelectronic subassembly disposed in the first implantable housing andcoupled to the at least one electrode, the electronic subassemblyconfigured and arranged to generate electrical pulses at the at leastone electrode to stimulate tissue adjacent to the microstimulator unitwhen implanted, the electronic subassembly comprising a processorconfigured and arranged to control timing and electrical characteristicsof the generated electrical pulses; an implantable battery unitcomprising a second housing, and a power source disposed in the secondhousing, wherein the power source is configured and arranged to providepower for operation of the processor in each of the plurality ofimplantable microstimulator units and to provide power for theelectrical pulses generated at the at least one electrode of each of theplurality of microstimulator units, wherein the implantable battery unitis separate from the plurality of implantable microstimulator units; aplurality of leads coupling the plurality of microstimulator units tothe battery unit to provide the power from the power source in thebattery unit to each of the microstimulator units: and at least one leadconnector, separate from the implantable battery unit and the pluralityof microstimulator units, disposed between the implantable battery unitand at least one of the implantable microstimulator units and configuredand arranged to receive and electrically couple at least two of theplurality of leads to allow electrical signals from one lead to be to betransmitted to another lead.
 2. The implantable microstimulatorarrangement of claim 1, wherein the implantable battery unit furthercomprises an antenna.
 3. The implantable microstimulator arrangement ofclaim 2, wherein the processor is coupled to a receiver in communicationwith the antenna.
 4. The implantable microstimulator arrangement ofclaim 1, wherein the implantable microstimulator arrangement comprisesat least three implantable microstimulator units, wherein eachmicrostimulator unit is configured and arranged to stimulate the tissueadjacent that microstimulator unit using the electrical pulses generatedby the electronic subassembly of that microstimulator unit.
 5. Theimplantable microstimulator arrangement of claim 1, wherein theimplantable microstimulator arrangement comprises a plurality of thelead connectors separate from the implantable battery unit and theplurality of microstimulator units, wherein each lead connector isconfigured and arranged to receive and electrically couple at least twoof the plurality of leads to allow electrical signals from one lead tobe transmitted to another lead.
 6. The implantable microstimulatorarrangement of claim 1, wherein a one of the plurality of implantablemicrostimulator units further comprises an antenna disposed in the firsthousing.
 7. The implantable microstimulator arrangement of claim 1,wherein a one of the plurality of leads is removably coupled to thebattery unit.
 8. The implantable microstimulator arrangement of claim 1,wherein a one of the plurality of leads is removably coupled to a one ofthe plurality of microstimulator units.
 9. The implantablemicrostimulator arrangement of claim 1, wherein the plurality of leadscomprises at least three leads and wherein the at least one leadconnector is configured and arranged to receive and electrically couplethe at least three leads to allow electrical signals from one lead to betransmitted to another lead.
 10. The implantable microstimulatorarrangement of claim 1, wherein the processor is configured to produce asignal to begin charging the battery.
 11. The implantablemicrostimulator arrangement of claim 1, wherein the implantablemicrostimulator arrangement comprises a plurality of battery units,wherein each of the battery units is coupled to a remainder of themicrostimulator arrangement using a different one of the plurality ofleads.
 12. The implantable microstimulator arrangement of claim 1,wherein the battery unit comprises an indifferent electrode.
 13. Theimplantable microstimulator arrangement of claim 1, wherein at least oneof the lead connectors comprises an indifferent electrode.
 14. Theimplantable microstimulator arrangement of claim 1, wherein at least oneof the lead connectors is configured and arranged to connect to at leastthree leads.
 15. The implantable microstimulator arrangement of claim 1,wherein each of the lead connectors is configured and arranged toconnect to at least three leads.
 16. The implantable microstimulatorarrangement of claim 1, wherein the first housing of each of themicrostimulator units has a cylindrical shape and a diameter of up to 8mm.
 17. An implantable microstimulator arrangement, comprising: at leastone implantable battery unit comprising a first housing, and a powersource disposed in the first housing; a plurality of implantablemicrostimulator units, wherein each implantable microstimulator unitcomprises a second housing, at least one electrode disposed on, or aspart of, the second housing, and an electronic subassembly disposed inthe second housing and coupled to the at least one electrode, theelectronic subassembly configured and arranged to generate electricalpulses at the at least one electrode to stimulate tissue adjacent themicrostimulator unit when implanted, the electronic subassemblycomprising a processor configured and arranged to control timing andelectrical characteristics of the generated electrical pulses, whereinthe power source of the at least one implantable battery unit isconfigured and arranged to provide power for operation of the processorin each of the plurality of implantable microstimulator units and toprovide power for the electrical pulses generated at the at least oneelectrode of each of the plurality of microstimulator units; a pluralityof lead connectors separate from the implantable battery unit and theplurality of microstimulator units, wherein each lead connector isconfigured and arranged to receive and electrically couple at leastthree leads to allow electrical signals from one lead to be transmittedto another lead; and a plurality of leads that couple themicrostimulator units to the at least one battery unit using the leadconnectors to provide power from the power source in the battery unit toeach of the microstimulator units; wherein the at least one implantablebattery unit is separate from the plurality of implantablemicrostimulator units.
 18. A method of treating body tissue, the methodcomprising: implanting a plurality of microstimulator units into a bodyin the proximity of the body tissue to be treated, each microstimulatorunit comprising a first housing, at least one electrode disposed on, oras part of, the first housing, and an electronic subassembly disposed inthe first housing and coupled to the at least one electrode, theelectronic subassembly configured and arranged to generate electricalpulses at the at least one electrode to stimulate the body tissue, theelectronic subassembly comprising a processor configured and arranged tocontrol timing and electrical characteristics of the generatedelectrical pulses; implanting a separate battery unit into the body, thebattery unit comprising a second implantable housing and a power sourcedisposed in the second implantable housing, wherein the power source ofthe at least one implantable battery unit is configured and arranged toprovide power for operation of the processor in each of the plurality ofimplantable microstimulator units and to provide power for theelectrical pulses generated at the at least one electrode of each of theplurality of microstimulator units; coupling the battery unit to themicrostimulator units using a plurality of leads and at least one leadconnector to provide power from the power source in the battery unit toeach of the microstimulator units, wherein the at least one leadconnector is disposed between the implantable battery unit and at leastone of the implantable microstimulator units and configured and arrangedto receive and electrically couple at least two of the plurality ofleads to allow electrical signals from one lead to be to be transmittedto another lead; and operating the microstimulator units to treat thebody tissue.
 19. The method of claim 18, further comprising replacingthe battery unit without removing the microstimulator units.